// SPDX-License-Identifier: GPL-2.0-only
/*
 *	fs/libfs.c
 *	Library for filesystems writers.
 */

#include <generated/deconfig.h>
#include <linux/blkdev.h>
#include <linux/export.h>
#include <linux/pagemap.h>
#include <linux/slab.h>
#include <linux/cred.h>
#include <linux/mount.h>
#include <linux/vfs.h>
#include <linux/quotaops.h>
#include <linux/mutex.h>
#include <linux/namei.h>
#include <linux/exportfs.h>
#include <linux/writeback.h>
#include <linux/buffer_head.h> /* sync_mapping_buffers */
#include <linux/fs_context.h>
#include <linux/pseudo_fs.h>
#include <linux/fsnotify.h>
#include <linux/unicode.h>
#include <linux/fscrypt.h>

#include <linux/uaccess.h>

#include "internal.h"

//int simple_getattr(struct user_namespace *mnt_userns, const struct path *path,
//		   struct kstat *stat, u32 request_mask,
//		   unsigned int query_flags)
//{
//	struct inode *inode = d_inode(path->dentry);
//	generic_fillattr(&init_user_ns, inode, stat);
//	stat->blocks = inode->i_mapping->nrpages << (PAGE_SHIFT - 9);
//	return 0;
//}
//EXPORT_SYMBOL(simple_getattr);
//
//int simple_statfs(struct dentry *dentry, struct kstatfs *buf)
//{
//	buf->f_type = dentry->d_sb->s_magic;
//	buf->f_bsize = PAGE_SIZE;
//	buf->f_namelen = NAME_MAX;
//	return 0;
//}
//EXPORT_SYMBOL(simple_statfs);
//
///*
// * Retaining negative dentries for an in-memory filesystem just wastes
// * memory and lookup time: arrange for them to be deleted immediately.
// */
//int always_delete_dentry(const struct dentry *dentry)
//{
//	return 1;
//}
//EXPORT_SYMBOL(always_delete_dentry);
//
//const struct dentry_operations simple_dentry_operations = {
//	.d_delete = always_delete_dentry,
//};
//EXPORT_SYMBOL(simple_dentry_operations);
//
///*
// * Lookup the data. This is trivial - if the dentry didn't already
// * exist, we know it is negative.  Set d_op to delete negative dentries.
// */
//struct dentry *simple_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags)
//{
//	if (dentry->d_name.len > NAME_MAX)
//		return ERR_PTR(-ENAMETOOLONG);
//	if (!dentry->d_sb->s_d_op)
//		d_set_d_op(dentry, &simple_dentry_operations);
//	d_add(dentry, NULL);
//	return NULL;
//}
//EXPORT_SYMBOL(simple_lookup);
//
//int dcache_dir_open(struct inode *inode, struct file *file)
//{
//	file->private_data = d_alloc_cursor(file->f_path.dentry);
//
//	return file->private_data ? 0 : -ENOMEM;
//}
//EXPORT_SYMBOL(dcache_dir_open);
//
//int dcache_dir_close(struct inode *inode, struct file *file)
//{
//	dput(file->private_data);
//	return 0;
//}
//EXPORT_SYMBOL(dcache_dir_close);
//
///* parent is locked at least shared */
///*
// * Returns an element of siblings' list.
// * We are looking for <count>th positive after <p>; if
// * found, dentry is grabbed and returned to caller.
// * If no such element exists, NULL is returned.
// */
//static struct dentry *scan_positives(struct dentry *cursor,
//					struct list_head *p,
//					loff_t count,
//					struct dentry *last)
//{
//	struct dentry *dentry = cursor->d_parent, *found = NULL;
//
//	spin_lock(&dentry->d_lock);
//	while ((p = p->next) != &dentry->d_subdirs) {
//		struct dentry *d = list_entry(p, struct dentry, d_child);
//		// we must at least skip cursors, to avoid livelocks
//		if (d->d_flags & DCACHE_DENTRY_CURSOR)
//			continue;
//		if (simple_positive(d) && !--count) {
//			spin_lock_nested(&d->d_lock, DENTRY_D_LOCK_NESTED);
//			if (simple_positive(d))
//				found = dget_dlock(d);
//			spin_unlock(&d->d_lock);
//			if (likely(found))
//				break;
//			count = 1;
//		}
//		if (need_resched()) {
//			list_move(&cursor->d_child, p);
//			p = &cursor->d_child;
//			spin_unlock(&dentry->d_lock);
//			cond_resched();
//			spin_lock(&dentry->d_lock);
//		}
//	}
//	spin_unlock(&dentry->d_lock);
//	dput(last);
//	return found;
//}
//
//loff_t dcache_dir_lseek(struct file *file, loff_t offset, int whence)
//{
//	struct dentry *dentry = file->f_path.dentry;
//	switch (whence) {
//		case 1:
//			offset += file->f_pos;
//			fallthrough;
//		case 0:
//			if (offset >= 0)
//				break;
//			fallthrough;
//		default:
//			return -EINVAL;
//	}
//	if (offset != file->f_pos) {
//		struct dentry *cursor = file->private_data;
//		struct dentry *to = NULL;
//
//		inode_lock_shared(dentry->d_inode);
//
//		if (offset > 2)
//			to = scan_positives(cursor, &dentry->d_subdirs,
//					    offset - 2, NULL);
//		spin_lock(&dentry->d_lock);
//		if (to)
//			list_move(&cursor->d_child, &to->d_child);
//		else
//			list_del_init(&cursor->d_child);
//		spin_unlock(&dentry->d_lock);
//		dput(to);
//
//		file->f_pos = offset;
//
//		inode_unlock_shared(dentry->d_inode);
//	}
//	return offset;
//}
//EXPORT_SYMBOL(dcache_dir_lseek);
//
///* Relationship between i_mode and the DT_xxx types */
//static inline unsigned char dt_type(struct inode *inode)
//{
//	return (inode->i_mode >> 12) & 15;
//}
//
///*
// * Directory is locked and all positive dentries in it are safe, since
// * for ramfs-type trees they can't go away without unlink() or rmdir(),
// * both impossible due to the lock on directory.
// */
//
//int dcache_readdir(struct file *file, struct dir_context *ctx)
//{
//	struct dentry *dentry = file->f_path.dentry;
//	struct dentry *cursor = file->private_data;
//	struct list_head *anchor = &dentry->d_subdirs;
//	struct dentry *next = NULL;
//	struct list_head *p;
//
//	if (!dir_emit_dots(file, ctx))
//		return 0;
//
//	if (ctx->pos == 2)
//		p = anchor;
//	else if (!list_empty(&cursor->d_child))
//		p = &cursor->d_child;
//	else
//		return 0;
//
//	while ((next = scan_positives(cursor, p, 1, next)) != NULL) {
//		if (!dir_emit(ctx, next->d_name.name, next->d_name.len,
//			      d_inode(next)->i_ino, dt_type(d_inode(next))))
//			break;
//		ctx->pos++;
//		p = &next->d_child;
//	}
//	spin_lock(&dentry->d_lock);
//	if (next)
//		list_move_tail(&cursor->d_child, &next->d_child);
//	else
//		list_del_init(&cursor->d_child);
//	spin_unlock(&dentry->d_lock);
//	dput(next);
//
//	return 0;
//}
//EXPORT_SYMBOL(dcache_readdir);
//
//ssize_t generic_read_dir(struct file *filp, char __user *buf, size_t siz, loff_t *ppos)
//{
//	return -EISDIR;
//}
//EXPORT_SYMBOL(generic_read_dir);
//
//const struct file_operations simple_dir_operations = {
//	.open		= dcache_dir_open,
//	.release	= dcache_dir_close,
//	.llseek		= dcache_dir_lseek,
//	.read		= generic_read_dir,
//	.iterate_shared	= dcache_readdir,
//	.fsync		= noop_fsync,
//};
//EXPORT_SYMBOL(simple_dir_operations);
//
//const struct inode_operations simple_dir_inode_operations = {
//	.lookup		= simple_lookup,
//};
//EXPORT_SYMBOL(simple_dir_inode_operations);
//
//static struct dentry *find_next_child(struct dentry *parent, struct dentry *prev)
//{
//	struct dentry *child = NULL;
//	struct list_head *p = prev ? &prev->d_child : &parent->d_subdirs;
//
//	spin_lock(&parent->d_lock);
//	while ((p = p->next) != &parent->d_subdirs) {
//		struct dentry *d = container_of(p, struct dentry, d_child);
//		if (simple_positive(d)) {
//			spin_lock_nested(&d->d_lock, DENTRY_D_LOCK_NESTED);
//			if (simple_positive(d))
//				child = dget_dlock(d);
//			spin_unlock(&d->d_lock);
//			if (likely(child))
//				break;
//		}
//	}
//	spin_unlock(&parent->d_lock);
//	dput(prev);
//	return child;
//}
//
//void simple_recursive_removal(struct dentry *dentry,
//                              void (*callback)(struct dentry *))
//{
//	struct dentry *this = dget(dentry);
//	while (true) {
//		struct dentry *victim = NULL, *child;
//		struct inode *inode = this->d_inode;
//
//		inode_lock(inode);
//		if (d_is_dir(this))
//			inode->i_flags |= S_DEAD;
//		while ((child = find_next_child(this, victim)) == NULL) {
//			// kill and ascend
//			// update metadata while it's still locked
//			inode->i_ctime = current_time(inode);
//			clear_nlink(inode);
//			inode_unlock(inode);
//			victim = this;
//			this = this->d_parent;
//			inode = this->d_inode;
//			inode_lock(inode);
//			if (simple_positive(victim)) {
//				d_invalidate(victim);	// avoid lost mounts
//				if (d_is_dir(victim))
//					fsnotify_rmdir(inode, victim);
//				else
//					fsnotify_unlink(inode, victim);
//				if (callback)
//					callback(victim);
//				dput(victim);		// unpin it
//			}
//			if (victim == dentry) {
//				inode->i_ctime = inode->i_mtime =
//					current_time(inode);
//				if (d_is_dir(dentry))
//					drop_nlink(inode);
//				inode_unlock(inode);
//				dput(dentry);
//				return;
//			}
//		}
//		inode_unlock(inode);
//		this = child;
//	}
//}
//EXPORT_SYMBOL(simple_recursive_removal);
//
//static const struct super_operations simple_super_operations = {
//	.statfs		= simple_statfs,
//};
//
//static int pseudo_fs_fill_super(struct super_block *s, struct fs_context *fc)
//{
//	struct pseudo_fs_context *ctx = fc->fs_private;
//	struct inode *root;
//
//	s->s_maxbytes = MAX_LFS_FILESIZE;
//	s->s_blocksize = PAGE_SIZE;
//	s->s_blocksize_bits = PAGE_SHIFT;
//	s->s_magic = ctx->magic;
//	s->s_op = ctx->ops ?: &simple_super_operations;
//	s->s_xattr = ctx->xattr;
//	s->s_time_gran = 1;
//	root = new_inode(s);
//	if (!root)
//		return -ENOMEM;
//
//	/*
//	 * since this is the first inode, make it number 1. New inodes created
//	 * after this must take care not to collide with it (by passing
//	 * max_reserved of 1 to iunique).
//	 */
//	root->i_ino = 1;
//	root->i_mode = S_IFDIR | S_IRUSR | S_IWUSR;
//	root->i_atime = root->i_mtime = root->i_ctime = current_time(root);
//	s->s_root = d_make_root(root);
//	if (!s->s_root)
//		return -ENOMEM;
//	s->s_d_op = ctx->dops;
//	return 0;
//}
//
//static int pseudo_fs_get_tree(struct fs_context *fc)
//{
//	return get_tree_nodev(fc, pseudo_fs_fill_super);
//}
//
//static void pseudo_fs_free(struct fs_context *fc)
//{
//	kfree(fc->fs_private);
//}
//
//static const struct fs_context_operations pseudo_fs_context_ops = {
//	.free		= pseudo_fs_free,
//	.get_tree	= pseudo_fs_get_tree,
//};
//
///*
// * Common helper for pseudo-filesystems (sockfs, pipefs, bdev - stuff that
// * will never be mountable)
// */
//struct pseudo_fs_context *init_pseudo(struct fs_context *fc,
//					unsigned long magic)
//{
//	struct pseudo_fs_context *ctx;
//
//	ctx = kzalloc(sizeof(struct pseudo_fs_context), GFP_KERNEL);
//	if (likely(ctx)) {
//		ctx->magic = magic;
//		fc->fs_private = ctx;
//		fc->ops = &pseudo_fs_context_ops;
//		fc->sb_flags |= SB_NOUSER;
//		fc->global = true;
//	}
//	return ctx;
//}
//EXPORT_SYMBOL(init_pseudo);
//
//int simple_open(struct inode *inode, struct file *file)
//{
//	if (inode->i_private)
//		file->private_data = inode->i_private;
//	return 0;
//}
//EXPORT_SYMBOL(simple_open);
//
//int simple_link(struct dentry *old_dentry, struct inode *dir, struct dentry *dentry)
//{
//	struct inode *inode = d_inode(old_dentry);
//
//	inode->i_ctime = dir->i_ctime = dir->i_mtime = current_time(inode);
//	inc_nlink(inode);
//	ihold(inode);
//	dget(dentry);
//	d_instantiate(dentry, inode);
//	return 0;
//}
//EXPORT_SYMBOL(simple_link);
//
//int simple_empty(struct dentry *dentry)
//{
//	struct dentry *child;
//	int ret = 0;
//
//	spin_lock(&dentry->d_lock);
//	list_for_each_entry(child, &dentry->d_subdirs, d_child) {
//		spin_lock_nested(&child->d_lock, DENTRY_D_LOCK_NESTED);
//		if (simple_positive(child)) {
//			spin_unlock(&child->d_lock);
//			goto out;
//		}
//		spin_unlock(&child->d_lock);
//	}
//	ret = 1;
//out:
//	spin_unlock(&dentry->d_lock);
//	return ret;
//}
//EXPORT_SYMBOL(simple_empty);
//
//int simple_unlink(struct inode *dir, struct dentry *dentry)
//{
//	struct inode *inode = d_inode(dentry);
//
//	inode->i_ctime = dir->i_ctime = dir->i_mtime = current_time(inode);
//	drop_nlink(inode);
//	dput(dentry);
//	return 0;
//}
//EXPORT_SYMBOL(simple_unlink);
//
//int simple_rmdir(struct inode *dir, struct dentry *dentry)
//{
//	if (!simple_empty(dentry))
//		return -ENOTEMPTY;
//
//	drop_nlink(d_inode(dentry));
//	simple_unlink(dir, dentry);
//	drop_nlink(dir);
//	return 0;
//}
//EXPORT_SYMBOL(simple_rmdir);
//
//int simple_rename(struct user_namespace *mnt_userns, struct inode *old_dir,
//		  struct dentry *old_dentry, struct inode *new_dir,
//		  struct dentry *new_dentry, unsigned int flags)
//{
//	struct inode *inode = d_inode(old_dentry);
//	int they_are_dirs = d_is_dir(old_dentry);
//
//	if (flags & ~RENAME_NOREPLACE)
//		return -EINVAL;
//
//	if (!simple_empty(new_dentry))
//		return -ENOTEMPTY;
//
//	if (d_really_is_positive(new_dentry)) {
//		simple_unlink(new_dir, new_dentry);
//		if (they_are_dirs) {
//			drop_nlink(d_inode(new_dentry));
//			drop_nlink(old_dir);
//		}
//	} else if (they_are_dirs) {
//		drop_nlink(old_dir);
//		inc_nlink(new_dir);
//	}
//
//	old_dir->i_ctime = old_dir->i_mtime = new_dir->i_ctime =
//		new_dir->i_mtime = inode->i_ctime = current_time(old_dir);
//
//	return 0;
//}
//EXPORT_SYMBOL(simple_rename);
//
///**
// * simple_setattr - setattr for simple filesystem
// * @mnt_userns: user namespace of the target mount
// * @dentry: dentry
// * @iattr: iattr structure
// *
// * Returns 0 on success, -error on failure.
// *
// * simple_setattr is a simple ->setattr implementation without a proper
// * implementation of size changes.
// *
// * It can either be used for in-memory filesystems or special files
// * on simple regular filesystems.  Anything that needs to change on-disk
// * or wire state on size changes needs its own setattr method.
// */
//int simple_setattr(struct user_namespace *mnt_userns, struct dentry *dentry,
//		   struct iattr *iattr)
//{
//	struct inode *inode = d_inode(dentry);
//	int error;
//
//	error = setattr_prepare(mnt_userns, dentry, iattr);
//	if (error)
//		return error;
//
//	if (iattr->ia_valid & ATTR_SIZE)
//		truncate_setsize(inode, iattr->ia_size);
//	setattr_copy(mnt_userns, inode, iattr);
//	mark_inode_dirty(inode);
//	return 0;
//}
//EXPORT_SYMBOL(simple_setattr);
//
//int simple_readpage(struct file *file, struct page *page)
//{
//	clear_highpage(page);
//	flush_dcache_page(page);
//	SetPageUptodate(page);
//	unlock_page(page);
//	return 0;
//}
//EXPORT_SYMBOL(simple_readpage);
//
//int simple_write_begin(struct file *file, struct address_space *mapping,
//			loff_t pos, unsigned len, unsigned flags,
//			struct page **pagep, void **fsdata)
//{
//	struct page *page;
//	pgoff_t index;
//
//	index = pos >> PAGE_SHIFT;
//
//	page = grab_cache_page_write_begin(mapping, index, flags);
//	if (!page)
//		return -ENOMEM;
//
//	*pagep = page;
//
//	if (!PageUptodate(page) && (len != PAGE_SIZE)) {
//		unsigned from = pos & (PAGE_SIZE - 1);
//
//		zero_user_segments(page, 0, from, from + len, PAGE_SIZE);
//	}
//	return 0;
//}
//EXPORT_SYMBOL(simple_write_begin);
//
///**
// * simple_write_end - .write_end helper for non-block-device FSes
// * @file: See .write_end of address_space_operations
// * @mapping: 		"
// * @pos: 		"
// * @len: 		"
// * @copied: 		"
// * @page: 		"
// * @fsdata: 		"
// *
// * simple_write_end does the minimum needed for updating a page after writing is
// * done. It has the same API signature as the .write_end of
// * address_space_operations vector. So it can just be set onto .write_end for
// * FSes that don't need any other processing. i_mutex is assumed to be held.
// * Block based filesystems should use generic_write_end().
// * NOTE: Even though i_size might get updated by this function, mark_inode_dirty
// * is not called, so a filesystem that actually does store data in .write_inode
// * should extend on what's done here with a call to mark_inode_dirty() in the
// * case that i_size has changed.
// *
// * Use *ONLY* with simple_readpage()
// */
//int simple_write_end(struct file *file, struct address_space *mapping,
//			loff_t pos, unsigned len, unsigned copied,
//			struct page *page, void *fsdata)
//{
//	struct inode *inode = page->mapping->host;
//	loff_t last_pos = pos + copied;
//
//	/* zero the stale part of the page if we did a short copy */
//	if (!PageUptodate(page)) {
//		if (copied < len) {
//			unsigned from = pos & (PAGE_SIZE - 1);
//
//			zero_user(page, from + copied, len - copied);
//		}
//		SetPageUptodate(page);
//	}
//	/*
//	 * No need to use i_size_read() here, the i_size
//	 * cannot change under us because we hold the i_mutex.
//	 */
//	if (last_pos > inode->i_size)
//		i_size_write(inode, last_pos);
//
//	set_page_dirty(page);
//	unlock_page(page);
//	put_page(page);
//
//	return copied;
//}
//EXPORT_SYMBOL(simple_write_end);
//
///*
// * the inodes created here are not hashed. If you use iunique to generate
// * unique inode values later for this filesystem, then you must take care
// * to pass it an appropriate max_reserved value to avoid collisions.
// */
//int simple_fill_super(struct super_block *s, unsigned long magic,
//		      const struct tree_descr *files)
//{
//	struct inode *inode;
//	struct dentry *root;
//	struct dentry *dentry;
//	int i;
//
//	s->s_blocksize = PAGE_SIZE;
//	s->s_blocksize_bits = PAGE_SHIFT;
//	s->s_magic = magic;
//	s->s_op = &simple_super_operations;
//	s->s_time_gran = 1;
//
//	inode = new_inode(s);
//	if (!inode)
//		return -ENOMEM;
//	/*
//	 * because the root inode is 1, the files array must not contain an
//	 * entry at index 1
//	 */
//	inode->i_ino = 1;
//	inode->i_mode = S_IFDIR | 0755;
//	inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
//	inode->i_op = &simple_dir_inode_operations;
//	inode->i_fop = &simple_dir_operations;
//	set_nlink(inode, 2);
//	root = d_make_root(inode);
//	if (!root)
//		return -ENOMEM;
//	for (i = 0; !files->name || files->name[0]; i++, files++) {
//		if (!files->name)
//			continue;
//
//		/* warn if it tries to conflict with the root inode */
//		if (unlikely(i == 1))
//			printk(KERN_WARNING "%s: %s passed in a files array"
//				"with an index of 1!\n", __func__,
//				s->s_type->name);
//
//		dentry = d_alloc_name(root, files->name);
//		if (!dentry)
//			goto out;
//		inode = new_inode(s);
//		if (!inode) {
//			dput(dentry);
//			goto out;
//		}
//		inode->i_mode = S_IFREG | files->mode;
//		inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
//		inode->i_fop = files->ops;
//		inode->i_ino = i;
//		d_add(dentry, inode);
//	}
//	s->s_root = root;
//	return 0;
//out:
//	d_genocide(root);
//	shrink_dcache_parent(root);
//	dput(root);
//	return -ENOMEM;
//}
//EXPORT_SYMBOL(simple_fill_super);
//
//static DEFINE_SPINLOCK(pin_fs_lock);
//
//int simple_pin_fs(struct file_system_type *type, struct vfsmount **mount, int *count)
//{
//	struct vfsmount *mnt = NULL;
//	spin_lock(&pin_fs_lock);
//	if (unlikely(!*mount)) {
//		spin_unlock(&pin_fs_lock);
//		mnt = vfs_kern_mount(type, SB_KERNMOUNT, type->name, NULL);
//		if (IS_ERR(mnt))
//			return PTR_ERR(mnt);
//		spin_lock(&pin_fs_lock);
//		if (!*mount)
//			*mount = mnt;
//	}
//	mntget(*mount);
//	++*count;
//	spin_unlock(&pin_fs_lock);
//	mntput(mnt);
//	return 0;
//}
//EXPORT_SYMBOL(simple_pin_fs);
//
//void simple_release_fs(struct vfsmount **mount, int *count)
//{
//	struct vfsmount *mnt;
//	spin_lock(&pin_fs_lock);
//	mnt = *mount;
//	if (!--*count)
//		*mount = NULL;
//	spin_unlock(&pin_fs_lock);
//	mntput(mnt);
//}
//EXPORT_SYMBOL(simple_release_fs);

/**
 * simple_read_from_buffer - copy data from the buffer to user space
 * @to: the user space buffer to read to
 * @count: the maximum number of bytes to read
 * @ppos: the current position in the buffer
 * @from: the buffer to read from
 * @available: the size of the buffer
 *
 * The simple_read_from_buffer() function reads up to @count bytes from the
 * buffer @from at offset @ppos into the user space address starting at @to.
 *
 * On success, the number of bytes read is returned and the offset @ppos is
 * advanced by this number, or negative value is returned on error.
 **/
ssize_t simple_read_from_buffer(void __user *to, size_t count, loff_t *ppos,
				const void *from, size_t available)
{
	loff_t pos = *ppos;
	size_t ret;

	if (pos < 0)
		return -EINVAL;
	if (pos >= available || !count)
		return 0;
	if (count > available - pos)
		count = available - pos;
	ret = copy_to_user(to, from + pos, count);
	if (ret == count)
		return -EFAULT;
	count -= ret;
	*ppos = pos + count;
	return count;
}
EXPORT_SYMBOL(simple_read_from_buffer);

/**
 * simple_write_to_buffer - copy data from user space to the buffer
 * @to: the buffer to write to
 * @available: the size of the buffer
 * @ppos: the current position in the buffer
 * @from: the user space buffer to read from
 * @count: the maximum number of bytes to read
 *
 * The simple_write_to_buffer() function reads up to @count bytes from the user
 * space address starting at @from into the buffer @to at offset @ppos.
 *
 * On success, the number of bytes written is returned and the offset @ppos is
 * advanced by this number, or negative value is returned on error.
 **/
ssize_t simple_write_to_buffer(void *to, size_t available, loff_t *ppos,
		const void __user *from, size_t count)
{
	loff_t pos = *ppos;
	size_t res;

	if (pos < 0)
		return -EINVAL;
	if (pos >= available || !count)
		return 0;
	if (count > available - pos)
		count = available - pos;
	res = copy_from_user(to + pos, from, count);
	if (res == count)
		return -EFAULT;
	count -= res;
	*ppos = pos + count;
	return count;
}
EXPORT_SYMBOL(simple_write_to_buffer);

/**
 * memory_read_from_buffer - copy data from the buffer
 * @to: the kernel space buffer to read to
 * @count: the maximum number of bytes to read
 * @ppos: the current position in the buffer
 * @from: the buffer to read from
 * @available: the size of the buffer
 *
 * The memory_read_from_buffer() function reads up to @count bytes from the
 * buffer @from at offset @ppos into the kernel space address starting at @to.
 *
 * On success, the number of bytes read is returned and the offset @ppos is
 * advanced by this number, or negative value is returned on error.
 **/
ssize_t memory_read_from_buffer(void *to, size_t count, loff_t *ppos,
				const void *from, size_t available)
{
	loff_t pos = *ppos;

	if (pos < 0)
		return -EINVAL;
	if (pos >= available)
		return 0;
	if (count > available - pos)
		count = available - pos;
	memcpy(to, from + pos, count);
	*ppos = pos + count;

	return count;
}
EXPORT_SYMBOL(memory_read_from_buffer);

///*
// * Transaction based IO.
// * The file expects a single write which triggers the transaction, and then
// * possibly a read which collects the result - which is stored in a
// * file-local buffer.
// */
//
//void simple_transaction_set(struct file *file, size_t n)
//{
//	struct simple_transaction_argresp *ar = file->private_data;
//
//	BUG_ON(n > SIMPLE_TRANSACTION_LIMIT);
//
//	/*
//	 * The barrier ensures that ar->size will really remain zero until
//	 * ar->data is ready for reading.
//	 */
//	smp_mb();
//	ar->size = n;
//}
//EXPORT_SYMBOL(simple_transaction_set);
//
//char *simple_transaction_get(struct file *file, const char __user *buf, size_t size)
//{
//	struct simple_transaction_argresp *ar;
//	static DEFINE_SPINLOCK(simple_transaction_lock);
//
//	if (size > SIMPLE_TRANSACTION_LIMIT - 1)
//		return ERR_PTR(-EFBIG);
//
//	ar = (struct simple_transaction_argresp *)get_zeroed_page(GFP_KERNEL);
//	if (!ar)
//		return ERR_PTR(-ENOMEM);
//
//	spin_lock(&simple_transaction_lock);
//
//	/* only one write allowed per open */
//	if (file->private_data) {
//		spin_unlock(&simple_transaction_lock);
//		free_page((unsigned long)ar);
//		return ERR_PTR(-EBUSY);
//	}
//
//	file->private_data = ar;
//
//	spin_unlock(&simple_transaction_lock);
//
//	if (copy_from_user(ar->data, buf, size))
//		return ERR_PTR(-EFAULT);
//
//	return ar->data;
//}
//EXPORT_SYMBOL(simple_transaction_get);
//
//ssize_t simple_transaction_read(struct file *file, char __user *buf, size_t size, loff_t *pos)
//{
//	struct simple_transaction_argresp *ar = file->private_data;
//
//	if (!ar)
//		return 0;
//	return simple_read_from_buffer(buf, size, pos, ar->data, ar->size);
//}
//EXPORT_SYMBOL(simple_transaction_read);
//
//int simple_transaction_release(struct inode *inode, struct file *file)
//{
//	free_page((unsigned long)file->private_data);
//	return 0;
//}
//EXPORT_SYMBOL(simple_transaction_release);
//
///* Simple attribute files */
//
//struct simple_attr {
//	int (*get)(void *, u64 *);
//	int (*set)(void *, u64);
//	char get_buf[24];	/* enough to store a u64 and "\n\0" */
//	char set_buf[24];
//	void *data;
//	const char *fmt;	/* format for read operation */
//	struct mutex mutex;	/* protects access to these buffers */
//};
//
///* simple_attr_open is called by an actual attribute open file operation
// * to set the attribute specific access operations. */
//int simple_attr_open(struct inode *inode, struct file *file,
//		     int (*get)(void *, u64 *), int (*set)(void *, u64),
//		     const char *fmt)
//{
//	struct simple_attr *attr;
//
//	attr = kzalloc(sizeof(*attr), GFP_KERNEL);
//	if (!attr)
//		return -ENOMEM;
//
//	attr->get = get;
//	attr->set = set;
//	attr->data = inode->i_private;
//	attr->fmt = fmt;
//	mutex_init(&attr->mutex);
//
//	file->private_data = attr;
//
//	return nonseekable_open(inode, file);
//}
//EXPORT_SYMBOL_GPL(simple_attr_open);
//
//int simple_attr_release(struct inode *inode, struct file *file)
//{
//	kfree(file->private_data);
//	return 0;
//}
//EXPORT_SYMBOL_GPL(simple_attr_release);	/* GPL-only?  This?  Really? */
//
///* read from the buffer that is filled with the get function */
//ssize_t simple_attr_read(struct file *file, char __user *buf,
//			 size_t len, loff_t *ppos)
//{
//	struct simple_attr *attr;
//	size_t size;
//	ssize_t ret;
//
//	attr = file->private_data;
//
//	if (!attr->get)
//		return -EACCES;
//
//	ret = mutex_lock_interruptible(&attr->mutex);
//	if (ret)
//		return ret;
//
//	if (*ppos && attr->get_buf[0]) {
//		/* continued read */
//		size = strlen(attr->get_buf);
//	} else {
//		/* first read */
//		u64 val;
//		ret = attr->get(attr->data, &val);
//		if (ret)
//			goto out;
//
//		size = scnprintf(attr->get_buf, sizeof(attr->get_buf),
//				 attr->fmt, (unsigned long long)val);
//	}
//
//	ret = simple_read_from_buffer(buf, len, ppos, attr->get_buf, size);
//out:
//	mutex_unlock(&attr->mutex);
//	return ret;
//}
//EXPORT_SYMBOL_GPL(simple_attr_read);
//
///* interpret the buffer as a number to call the set function with */
//ssize_t simple_attr_write(struct file *file, const char __user *buf,
//			  size_t len, loff_t *ppos)
//{
//	struct simple_attr *attr;
//	unsigned long long val;
//	size_t size;
//	ssize_t ret;
//
//	attr = file->private_data;
//	if (!attr->set)
//		return -EACCES;
//
//	ret = mutex_lock_interruptible(&attr->mutex);
//	if (ret)
//		return ret;
//
//	ret = -EFAULT;
//	size = min(sizeof(attr->set_buf) - 1, len);
//	if (copy_from_user(attr->set_buf, buf, size))
//		goto out;
//
//	attr->set_buf[size] = '\0';
//	ret = kstrtoull(attr->set_buf, 0, &val);
//	if (ret)
//		goto out;
//	ret = attr->set(attr->data, val);
//	if (ret == 0)
//		ret = len; /* on success, claim we got the whole input */
//out:
//	mutex_unlock(&attr->mutex);
//	return ret;
//}
//EXPORT_SYMBOL_GPL(simple_attr_write);
//
///**
// * generic_fh_to_dentry - generic helper for the fh_to_dentry export operation
// * @sb:		filesystem to do the file handle conversion on
// * @fid:	file handle to convert
// * @fh_len:	length of the file handle in bytes
// * @fh_type:	type of file handle
// * @get_inode:	filesystem callback to retrieve inode
// *
// * This function decodes @fid as long as it has one of the well-known
// * Linux filehandle types and calls @get_inode on it to retrieve the
// * inode for the object specified in the file handle.
// */
//struct dentry *generic_fh_to_dentry(struct super_block *sb, struct fid *fid,
//		int fh_len, int fh_type, struct inode *(*get_inode)
//			(struct super_block *sb, u64 ino, u32 gen))
//{
//	struct inode *inode = NULL;
//
//	if (fh_len < 2)
//		return NULL;
//
//	switch (fh_type) {
//	case FILEID_INO32_GEN:
//	case FILEID_INO32_GEN_PARENT:
//		inode = get_inode(sb, fid->i32.ino, fid->i32.gen);
//		break;
//	}
//
//	return d_obtain_alias(inode);
//}
//EXPORT_SYMBOL_GPL(generic_fh_to_dentry);
//
///**
// * generic_fh_to_parent - generic helper for the fh_to_parent export operation
// * @sb:		filesystem to do the file handle conversion on
// * @fid:	file handle to convert
// * @fh_len:	length of the file handle in bytes
// * @fh_type:	type of file handle
// * @get_inode:	filesystem callback to retrieve inode
// *
// * This function decodes @fid as long as it has one of the well-known
// * Linux filehandle types and calls @get_inode on it to retrieve the
// * inode for the _parent_ object specified in the file handle if it
// * is specified in the file handle, or NULL otherwise.
// */
//struct dentry *generic_fh_to_parent(struct super_block *sb, struct fid *fid,
//		int fh_len, int fh_type, struct inode *(*get_inode)
//			(struct super_block *sb, u64 ino, u32 gen))
//{
//	struct inode *inode = NULL;
//
//	if (fh_len <= 2)
//		return NULL;
//
//	switch (fh_type) {
//	case FILEID_INO32_GEN_PARENT:
//		inode = get_inode(sb, fid->i32.parent_ino,
//				  (fh_len > 3 ? fid->i32.parent_gen : 0));
//		break;
//	}
//
//	return d_obtain_alias(inode);
//}
//EXPORT_SYMBOL_GPL(generic_fh_to_parent);
//
///**
// * __generic_file_fsync - generic fsync implementation for simple filesystems
// *
// * @file:	file to synchronize
// * @start:	start offset in bytes
// * @end:	end offset in bytes (inclusive)
// * @datasync:	only synchronize essential metadata if true
// *
// * This is a generic implementation of the fsync method for simple
// * filesystems which track all non-inode metadata in the buffers list
// * hanging off the address_space structure.
// */
//int __generic_file_fsync(struct file *file, loff_t start, loff_t end,
//				 int datasync)
//{
//	struct inode *inode = file->f_mapping->host;
//	int err;
//	int ret;
//
//	err = file_write_and_wait_range(file, start, end);
//	if (err)
//		return err;
//
//	inode_lock(inode);
//	ret = sync_mapping_buffers(inode->i_mapping);
//	if (!(inode->i_state & I_DIRTY_ALL))
//		goto out;
//	if (datasync && !(inode->i_state & I_DIRTY_DATASYNC))
//		goto out;
//
//	err = sync_inode_metadata(inode, 1);
//	if (ret == 0)
//		ret = err;
//
//out:
//	inode_unlock(inode);
//	/* check and advance again to catch errors after syncing out buffers */
//	err = file_check_and_advance_wb_err(file);
//	if (ret == 0)
//		ret = err;
//	return ret;
//}
//EXPORT_SYMBOL(__generic_file_fsync);
//
///**
// * generic_file_fsync - generic fsync implementation for simple filesystems
// *			with flush
// * @file:	file to synchronize
// * @start:	start offset in bytes
// * @end:	end offset in bytes (inclusive)
// * @datasync:	only synchronize essential metadata if true
// *
// */
//
//int generic_file_fsync(struct file *file, loff_t start, loff_t end,
//		       int datasync)
//{
//	struct inode *inode = file->f_mapping->host;
//	int err;
//
//	err = __generic_file_fsync(file, start, end, datasync);
//	if (err)
//		return err;
//	return blkdev_issue_flush(inode->i_sb->s_bdev);
//}
//EXPORT_SYMBOL(generic_file_fsync);
//
///**
// * generic_check_addressable - Check addressability of file system
// * @blocksize_bits:	log of file system block size
// * @num_blocks:		number of blocks in file system
// *
// * Determine whether a file system with @num_blocks blocks (and a
// * block size of 2**@blocksize_bits) is addressable by the sector_t
// * and page cache of the system.  Return 0 if so and -EFBIG otherwise.
// */
//int generic_check_addressable(unsigned blocksize_bits, u64 num_blocks)
//{
//	u64 last_fs_block = num_blocks - 1;
//	u64 last_fs_page =
//		last_fs_block >> (PAGE_SHIFT - blocksize_bits);
//
//	if (unlikely(num_blocks == 0))
//		return 0;
//
//	if ((blocksize_bits < 9) || (blocksize_bits > PAGE_SHIFT))
//		return -EINVAL;
//
//	if ((last_fs_block > (sector_t)(~0ULL) >> (blocksize_bits - 9)) ||
//	    (last_fs_page > (pgoff_t)(~0ULL))) {
//		return -EFBIG;
//	}
//	return 0;
//}
//EXPORT_SYMBOL(generic_check_addressable);
//
///*
// * No-op implementation of ->fsync for in-memory filesystems.
// */
//int noop_fsync(struct file *file, loff_t start, loff_t end, int datasync)
//{
//	return 0;
//}
//EXPORT_SYMBOL(noop_fsync);
//
//int noop_set_page_dirty(struct page *page)
//{
//	/*
//	 * Unlike __set_page_dirty_no_writeback that handles dirty page
//	 * tracking in the page object, dax does all dirty tracking in
//	 * the inode address_space in response to mkwrite faults. In the
//	 * dax case we only need to worry about potentially dirty CPU
//	 * caches, not dirty page cache pages to write back.
//	 *
//	 * This callback is defined to prevent fallback to
//	 * __set_page_dirty_buffers() in set_page_dirty().
//	 */
//	return 0;
//}
//EXPORT_SYMBOL_GPL(noop_set_page_dirty);
//
//void noop_invalidatepage(struct page *page, unsigned int offset,
//		unsigned int length)
//{
//	/*
//	 * There is no page cache to invalidate in the dax case, however
//	 * we need this callback defined to prevent falling back to
//	 * block_invalidatepage() in do_invalidatepage().
//	 */
//}
//EXPORT_SYMBOL_GPL(noop_invalidatepage);
//
//ssize_t noop_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
//{
//	/*
//	 * iomap based filesystems support direct I/O without need for
//	 * this callback. However, it still needs to be set in
//	 * inode->a_ops so that open/fcntl know that direct I/O is
//	 * generally supported.
//	 */
//	return -EINVAL;
//}
//EXPORT_SYMBOL_GPL(noop_direct_IO);
//
///* Because kfree isn't assignment-compatible with void(void*) ;-/ */
//void kfree_link(void *p)
//{
//	kfree(p);
//}
//EXPORT_SYMBOL(kfree_link);
//
///*
// * nop .set_page_dirty method so that people can use .page_mkwrite on
// * anon inodes.
// */
//static int anon_set_page_dirty(struct page *page)
//{
//	return 0;
//};
//
//struct inode *alloc_anon_inode(struct super_block *s)
//{
//	static const struct address_space_operations anon_aops = {
//		.set_page_dirty = anon_set_page_dirty,
//	};
//	struct inode *inode = new_inode_pseudo(s);
//
//	if (!inode)
//		return ERR_PTR(-ENOMEM);
//
//	inode->i_ino = get_next_ino();
//	inode->i_mapping->a_ops = &anon_aops;
//
//	/*
//	 * Mark the inode dirty from the very beginning,
//	 * that way it will never be moved to the dirty
//	 * list because mark_inode_dirty() will think
//	 * that it already _is_ on the dirty list.
//	 */
//	inode->i_state = I_DIRTY;
//	inode->i_mode = S_IRUSR | S_IWUSR;
//	inode->i_uid = current_fsuid();
//	inode->i_gid = current_fsgid();
//	inode->i_flags |= S_PRIVATE;
//	inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
//	return inode;
//}
//EXPORT_SYMBOL(alloc_anon_inode);
//
///**
// * simple_nosetlease - generic helper for prohibiting leases
// * @filp: file pointer
// * @arg: type of lease to obtain
// * @flp: new lease supplied for insertion
// * @priv: private data for lm_setup operation
// *
// * Generic helper for filesystems that do not wish to allow leases to be set.
// * All arguments are ignored and it just returns -EINVAL.
// */
//int
//simple_nosetlease(struct file *filp, long arg, struct file_lock **flp,
//		  void **priv)
//{
//	return -EINVAL;
//}
//EXPORT_SYMBOL(simple_nosetlease);
//
///**
// * simple_get_link - generic helper to get the target of "fast" symlinks
// * @dentry: not used here
// * @inode: the symlink inode
// * @done: not used here
// *
// * Generic helper for filesystems to use for symlink inodes where a pointer to
// * the symlink target is stored in ->i_link.  NOTE: this isn't normally called,
// * since as an optimization the path lookup code uses any non-NULL ->i_link
// * directly, without calling ->get_link().  But ->get_link() still must be set,
// * to mark the inode_operations as being for a symlink.
// *
// * Return: the symlink target
// */
//const char *simple_get_link(struct dentry *dentry, struct inode *inode,
//			    struct delayed_call *done)
//{
//	return inode->i_link;
//}
//EXPORT_SYMBOL(simple_get_link);
//
//const struct inode_operations simple_symlink_inode_operations = {
//	.get_link = simple_get_link,
//};
//EXPORT_SYMBOL(simple_symlink_inode_operations);
//
///*
// * Operations for a permanently empty directory.
// */
//static struct dentry *empty_dir_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags)
//{
//	return ERR_PTR(-ENOENT);
//}
//
//static int empty_dir_getattr(struct user_namespace *mnt_userns,
//			     const struct path *path, struct kstat *stat,
//			     u32 request_mask, unsigned int query_flags)
//{
//	struct inode *inode = d_inode(path->dentry);
//	generic_fillattr(&init_user_ns, inode, stat);
//	return 0;
//}
//
//static int empty_dir_setattr(struct user_namespace *mnt_userns,
//			     struct dentry *dentry, struct iattr *attr)
//{
//	return -EPERM;
//}
//
//static ssize_t empty_dir_listxattr(struct dentry *dentry, char *list, size_t size)
//{
//	return -EOPNOTSUPP;
//}
//
//static const struct inode_operations empty_dir_inode_operations = {
//	.lookup		= empty_dir_lookup,
//	.permission	= generic_permission,
//	.setattr	= empty_dir_setattr,
//	.getattr	= empty_dir_getattr,
//	.listxattr	= empty_dir_listxattr,
//};
//
//static loff_t empty_dir_llseek(struct file *file, loff_t offset, int whence)
//{
//	/* An empty directory has two entries . and .. at offsets 0 and 1 */
//	return generic_file_llseek_size(file, offset, whence, 2, 2);
//}
//
//static int empty_dir_readdir(struct file *file, struct dir_context *ctx)
//{
//	dir_emit_dots(file, ctx);
//	return 0;
//}
//
//static const struct file_operations empty_dir_operations = {
//	.llseek		= empty_dir_llseek,
//	.read		= generic_read_dir,
//	.iterate_shared	= empty_dir_readdir,
//	.fsync		= noop_fsync,
//};
//
//
//void make_empty_dir_inode(struct inode *inode)
//{
//	set_nlink(inode, 2);
//	inode->i_mode = S_IFDIR | S_IRUGO | S_IXUGO;
//	inode->i_uid = GLOBAL_ROOT_UID;
//	inode->i_gid = GLOBAL_ROOT_GID;
//	inode->i_rdev = 0;
//	inode->i_size = 0;
//	inode->i_blkbits = PAGE_SHIFT;
//	inode->i_blocks = 0;
//
//	inode->i_op = &empty_dir_inode_operations;
//	inode->i_opflags &= ~IOP_XATTR;
//	inode->i_fop = &empty_dir_operations;
//}
//
//bool is_empty_dir_inode(struct inode *inode)
//{
//	return (inode->i_fop == &empty_dir_operations) &&
//		(inode->i_op == &empty_dir_inode_operations);
//}
//
//#ifdef CONFIG_UNICODE
///*
// * Determine if the name of a dentry should be casefolded.
// *
// * Return: if names will need casefolding
// */
//static bool needs_casefold(const struct inode *dir)
//{
//	return IS_CASEFOLDED(dir) && dir->i_sb->s_encoding;
//}
//
///**
// * generic_ci_d_compare - generic d_compare implementation for casefolding filesystems
// * @dentry:	dentry whose name we are checking against
// * @len:	len of name of dentry
// * @str:	str pointer to name of dentry
// * @name:	Name to compare against
// *
// * Return: 0 if names match, 1 if mismatch, or -ERRNO
// */
//static int generic_ci_d_compare(const struct dentry *dentry, unsigned int len,
//				const char *str, const struct qstr *name)
//{
//	const struct dentry *parent = READ_ONCE(dentry->d_parent);
//	const struct inode *dir = READ_ONCE(parent->d_inode);
//	const struct super_block *sb = dentry->d_sb;
//	const struct unicode_map *um = sb->s_encoding;
//	struct qstr qstr = QSTR_INIT(str, len);
//	char strbuf[DNAME_INLINE_LEN];
//	int ret;
//
//	if (!dir || !needs_casefold(dir))
//		goto fallback;
//	/*
//	 * If the dentry name is stored in-line, then it may be concurrently
//	 * modified by a rename.  If this happens, the VFS will eventually retry
//	 * the lookup, so it doesn't matter what ->d_compare() returns.
//	 * However, it's unsafe to call utf8_strncasecmp() with an unstable
//	 * string.  Therefore, we have to copy the name into a temporary buffer.
//	 */
//	if (len <= DNAME_INLINE_LEN - 1) {
//		memcpy(strbuf, str, len);
//		strbuf[len] = 0;
//		qstr.name = strbuf;
//		/* prevent compiler from optimizing out the temporary buffer */
//		barrier();
//	}
//	ret = utf8_strncasecmp(um, name, &qstr);
//	if (ret >= 0)
//		return ret;
//
//	if (sb_has_strict_encoding(sb))
//		return -EINVAL;
//fallback:
//	if (len != name->len)
//		return 1;
//	return !!memcmp(str, name->name, len);
//}
//
///**
// * generic_ci_d_hash - generic d_hash implementation for casefolding filesystems
// * @dentry:	dentry of the parent directory
// * @str:	qstr of name whose hash we should fill in
// *
// * Return: 0 if hash was successful or unchanged, and -EINVAL on error
// */
//static int generic_ci_d_hash(const struct dentry *dentry, struct qstr *str)
//{
//	const struct inode *dir = READ_ONCE(dentry->d_inode);
//	struct super_block *sb = dentry->d_sb;
//	const struct unicode_map *um = sb->s_encoding;
//	int ret = 0;
//
//	if (!dir || !needs_casefold(dir))
//		return 0;
//
//	ret = utf8_casefold_hash(um, dentry, str);
//	if (ret < 0 && sb_has_strict_encoding(sb))
//		return -EINVAL;
//	return 0;
//}
//
//static const struct dentry_operations generic_ci_dentry_ops = {
//	.d_hash = generic_ci_d_hash,
//	.d_compare = generic_ci_d_compare,
//};
//#endif
//
//#ifdef CONFIG_FS_ENCRYPTION
//static const struct dentry_operations generic_encrypted_dentry_ops = {
//	.d_revalidate = fscrypt_d_revalidate,
//};
//#endif
//
//#if defined(CONFIG_FS_ENCRYPTION) && defined(CONFIG_UNICODE)
//static const struct dentry_operations generic_encrypted_ci_dentry_ops = {
//	.d_hash = generic_ci_d_hash,
//	.d_compare = generic_ci_d_compare,
//	.d_revalidate = fscrypt_d_revalidate,
//};
//#endif
//
///**
// * generic_set_encrypted_ci_d_ops - helper for setting d_ops for given dentry
// * @dentry:	dentry to set ops on
// *
// * Casefolded directories need d_hash and d_compare set, so that the dentries
// * contained in them are handled case-insensitively.  Note that these operations
// * are needed on the parent directory rather than on the dentries in it, and
// * while the casefolding flag can be toggled on and off on an empty directory,
// * dentry_operations can't be changed later.  As a result, if the filesystem has
// * casefolding support enabled at all, we have to give all dentries the
// * casefolding operations even if their inode doesn't have the casefolding flag
// * currently (and thus the casefolding ops would be no-ops for now).
// *
// * Encryption works differently in that the only dentry operation it needs is
// * d_revalidate, which it only needs on dentries that have the no-key name flag.
// * The no-key flag can't be set "later", so we don't have to worry about that.
// *
// * Finally, to maximize compatibility with overlayfs (which isn't compatible
// * with certain dentry operations) and to avoid taking an unnecessary
// * performance hit, we use custom dentry_operations for each possible
// * combination rather than always installing all operations.
// */
//void generic_set_encrypted_ci_d_ops(struct dentry *dentry)
//{
//#ifdef CONFIG_FS_ENCRYPTION
//	bool needs_encrypt_ops = dentry->d_flags & DCACHE_NOKEY_NAME;
//#endif
//#ifdef CONFIG_UNICODE
//	bool needs_ci_ops = dentry->d_sb->s_encoding;
//#endif
//#if defined(CONFIG_FS_ENCRYPTION) && defined(CONFIG_UNICODE)
//	if (needs_encrypt_ops && needs_ci_ops) {
//		d_set_d_op(dentry, &generic_encrypted_ci_dentry_ops);
//		return;
//	}
//#endif
//#ifdef CONFIG_FS_ENCRYPTION
//	if (needs_encrypt_ops) {
//		d_set_d_op(dentry, &generic_encrypted_dentry_ops);
//		return;
//	}
//#endif
//#ifdef CONFIG_UNICODE
//	if (needs_ci_ops) {
//		d_set_d_op(dentry, &generic_ci_dentry_ops);
//		return;
//	}
//#endif
//}
//EXPORT_SYMBOL(generic_set_encrypted_ci_d_ops);
